1. Field of the Invention
The present invention relates to a honeycomb structured body used as a filter for removing particulates and the like contained in exhaust gases, a catalyst supporting member, and the like.
2. Discussion of the Background
In recent years, particulates such as soot and the like contained in exhaust gases discharged from internal combustion engines of vehicles, such as buses and trucks, and construction machines, have raised serious problems as those particulates are harmful to the environment and the human body.
There have been proposed various honeycomb structured bodies made from porous ceramics, which serve as filters capable of collecting particulates in exhaust gases to convert the exhaust gases.
Conventionally, with respect to the honeycomb structured body of this type, a filter having the following structure has been proposed: two kinds of through holes, that is, a group of through holes with a relatively large capacity (hereinafter, referred to as large-capacity through hole) and a group of through holes with a relatively small capacity (hereinafter, referred to as small-capacity through hole), are prepared, and each of the large-capacity through holes is sealed with a plug at one of ends, and each of the small-capacity through holes is sealed with a plug at the other opposite end. Moreover, the honeycomb structured body that is designed to have another structure in which the large-capacity through hole has an opening on a gas inlet side of a filter while the small-capacity through hole has an opening on a gas outlet side of the filter has been proposed (for example, see JP-A56-124418, JP-A62-96717, JUM-A58-92409, U.S. Pat. No. 4,416,676, JP-A 58-196820, U.S. Pat. No. 4,420,316, JP-A 58-150015, JP-A 5-68828, French Patent No. 2789327, International Publication No. WO02/100514, International Publication No. WO02/10562, and International Publication No. WO03/20407).
There have been also known filters and the like having a structure in which the number of through holes that have openings on the gas inlet side (hereinafter, referred to as inlet-side through holes) is made greater than the number of through holes that have openings on the gas outlet side (hereinafter, referred to as outlet-side through holes) so that the total amount of surface areas on the inlet-side through holes is made relatively greater than the total amount of surface areas on the outlet-side through holes (for example, see FIG. 3 of JP-A 58-196820).
When viewed from the end face, these honeycomb structured bodies are constituted by two types of through holes, that is, a group of large-capacity through holes (the total amount of rates of surface area/cross-sectional area of the through holes is relatively large) and a group of small-capacity through holes (the total amount of rates of surface area/cross-sectional area of the through holes is relatively small).
The contents of JP-A 56-124418, JP-A 62-96717, JUM-A 58-92409, U.S. Pat. No. 4,416,676, JP-A 58-196820, U.S. Pat. No. 4,420,316, JP-A58-150015, JP-A5-68828, French Patent No. 2789327, International Publication No. WO02/100514, International Publication No. WO02/10562, and International Publication No. WO03/20407 are incorporated herein by reference in their entirety.